This invention relates to a boom articulation assembly or apparatus for aerial boom sections and particularly to a interconnection between the boom sections for articulating a vertical rotation of an upper boom relative to a lower boom and providing for positioning through angles of articulation up to 275 degrees.
Mobile aerial devices are well known for various applications. The aerial device generally include a first boom which is pivotally supported to a pedestal of a mobile support. The first boom is supported for pivoting upwardly from the mobile support. The second boom is pivotably coupled to the outer end of the first boom for pivotal movement into a collapsed storage position and for extension of the second boom from the first boom. The second boom is mounted for pivoting about the outer-end position of the first boom. A work platform, such as a bucket or basket, is generally pivotally mounted to the outer end of the second boom for supporting equipment and/or personnel for servicing of raised or elevated devices. Thus, mobile aerial devices are commonly used in the construction and servicing of overhead lighting systems; raised signs, tree trimming and other similar applications. Each boom may be a single member boom, telescoping boom member and may include additional booms connected to the lower or upper boom.
The ability of an articulating system to vary the angle between the upper and lower booms is significant in producing the versatility desired or necessary for workers to reach various areas of the work area without the need for continuously repositioning of the mobile support. Such articulation systems permits locating of the mobile support in a convenient stable position relative to the actual raised work area. The increased upper boom articulation allows the workers to reach some positions from two angular positions of the lower boom. If access is prohibited by obstructions such as power of telephone lines, trees, or structures for one position of the lower boom, an alternate articulation will permit a safe access. For example, with the lower boom raised 45 degrees and the upper boom open 95 degrees, the operator could reach a position directly over head. The same position could be reached with the lower boom raised 135 degrees from the stowed position and the upper boom open 265 degrees from the lower boom.
The prior art has disclosed various chain and cable or multiple pivoting link connections between the booms in combination with hydraulic cylinder units for the relative articulation of the booms. Alternate systems have disclosed various linkages interconnecting of the booms to each other in combination with operating cylinder units.
In practice, the booms are mounted for a collapsed storage positioning with the upper booms located in side-by-side relation above the lower boom. Alternatively, the upper boom can be stored in stacked relationship to the lower boom.